/Engine/Plugins/Experimental/GeometryScripting/Source/GeometryScriptingCore/Public/GeometryScript/GeometryScriptSelectionTypes.h
Combine SelectionB with current selection, updating current selection, using CombineMode to control how combining happens
void CombineSelectionInPlace ( const [FGeometryScriptMeshSelection](API\Plugins\GeometryScriptingCore\GeometryScript\FGeometryScriptMeshSelection) & SelectionB, [EGeometryScriptCombineSelectionMode](API\Plugins\GeometryScriptingCore\GeometryScript\EGeometryScriptC-_1) CombineMode )